zotero: Fix build on x86_64-darwin

When setting a non-`source` update channel, the build fails on
x86_64-darwin.

The build fails with:
```
source not found twice in ChannelPrefs

source

stringWithCString:encoding:
```
Which definitely means it is caused by the strings command here.

When manually executing the strings command on the file, I can repeat
getting only one `source` result on x86 mac, while getting two on arm64
or linux. After digging around, I tried with the flag `-arch all`, and
both `source` values are found on x86 mac. Full command: `strings -n 3
-arch all $binary`.

Also reported to upstream in https://github.com/zotero/zotero/pull/5926

pkgs/by-name/zo/zotero/fix-x86_64-darwin.patch

@@ -0,0 +1,13 @@
+diff --git a/app/mac/set-channel-prefs-channel b/app/mac/set-channel-prefs-channel
+index 2431837584..ab85d7e5c0 100755
+--- a/app/mac/set-channel-prefs-channel
++++ b/app/mac/set-channel-prefs-channel
+@@ -19,7 +19,7 @@ binary=$1
+ from_channel=$2
+ to_channel=$3
+ # `strings` has a 4-character minimum by default, but we need 3 for 'dev'
+-strings_cmd="strings -n 3"
++strings_cmd="strings -n 3 -arch all"
+
+ if [ ${#to_channel} -gt 7 ]; then
+        echo "Channel length cannot exceed 7 characters -- aborting" >&2

pkgs/by-name/zo/zotero/package.nix

@@ -193,6 +193,7 @@ buildNpmPackage (finalAttrs: {
     ./js-build-fixes.patch
     ./avoid-xulrunner-fetch.patch
     ./build-fixes.patch
+    ./fix-x86_64-darwin.patch
   ];
 
   postPatch = ''